Ononin’s Antagonistic Activity towards TRPV1: Insights from Molecular Dynamics and Capsaicin-Evoked Calcium Response in DRG Neurons

The search for effective painkillers has led to intensive research, with a particular focus on the transient receptor potential vanilloid-1 (TRPV1) channel as a possible target. One promising candidate is ononin, which is investigated for its binding with TRPV1 through a 200-ns molecular dynamic simulation and analysed via root-meansquare deviation (RMSD), root-mean-square fluctuation (RMSF), hydrogen-bond interactions, radius of gyration (RadGyr), and MM-PBSA energy calculations. The results were further validated experimentally via calcium imaging studies. Molecular dynamics revealed that the ononin-TRPV1 complex achieved stable binding within a remarkably short time of approximately 38 ns while maintaining the degree of compactness of the receptor throughout a 200 ns simulation period. In contrast, the capsazepine-TRPV1 complex displayed more significant structural deviations during the whole simulation. Moreover, MM-PBSA energy calculations showed a relatively strong binding affinity between ononin and TRPV1, mainly attributed to favourable hydrophobic interactions. Pre-incubation of dorsal root ganglia (DRG) neurons with ononin (1 and 10 μM) or capsazepine (10 μM) for 4 min prior to stimulation with capsaicin significantly reduced capsaicin-evoked calcium responses. No significant difference between capsazepine and ononin was found at a concentration of 10 μM. Overall, this research demonstrates the potential of ononin as a potential antagonist for developing analgesics targeting TRPV1. Hence, and to our best knowledge, this study represents the first report of ononin's antagonistic activity towards TRPV1.